1. Field of the Invention
This invention relates in general to drive systems and more particularly to a drive system having an optionally operable power input subsystem which regulates the amount of power input to the system in accordance with the demand placed thereon and apportions the input power in accordance with individual loads placed on the system by driven entities.
2. Description of the Prior Art
Drive systems have traditionally been employed for coupling a drive means to a driven mechanism and will vary in complexity in accordance with the particular components of the system, the use, and the degree of control needed or desired. For example, a very simple driven system may include an internal combustion engine the output of which is coupled by a chain sprocket arrangement to drive a circular saw. A good example of a more complex drive system is the well known drive train of an automotive vehicle. These traditional drive systems, regardless of complexity, all work toward the accomplishment of a very simple objective; namely, the connection of a single drive means to a single driven mechanism, and this may be seen upon considering the above examples. In the first example, the engine simply drives the saw and in the second example, the engine drives the wheels of the automotive vehicle.
It has been known for many years that the traditional drive systems in general, and the automotive drive trains in particular, are very inefficient in their use of fuel and contribute significantly to environmental pollution. More recently, environmental considerations along with fossil fuel availabilities and costs, have drawn considerable attention to these known deficiencies and drawbacks, and many attempts have been made to develop a drive system which uses no fossil fuel and is nonpolluting. A known way of accomplishing such objectives is with a purely electric drive. However, due to storage battery limitations, electrically operated vehicles have received very limited commercial acceptance.
As a result of the known drawbacks of the traditional drive systems and electric drive systems, attempts have been made to combine the two to produce a hybrid system that reduces the drawbacks of the two separate systems.
A number of patents have been issued which disclose such hybrid systems as including an internal combustion engine, an electric traction motor, a generator, a battery and a mechanical gear transmission. These hybrid prior art systems have been configured in various ways in attempts to solve the above mentioned problems, and none have achieved a degree of success which is significant enough to warrant anything more than very limited production.
To the best of my knowledge, the prior art hybrid system most closely related to the instant invention is disclosed in U.S. Pat. No. 3,566,717 issued on Mar. 2, 1971 to Berman et al. This particular prior art drive system includes an internal combustion engine the output shaft of which is connected to drive the sun gear of a planetary gear train. The planet gears of the train are mounted on a planet carrier which is in the form of a gear and power is taken off of that gear to drive a generator. The ring gear of the planetary gear train powers the system output shaft which carries a gear to couple a motor-generator thereto. In this prior art system, the internal combustion engine is running at all times as the main source of power, and the generator operates to charge the batteries only when the vehicle is accelerating and must be locked out of the system when the vehicle is at cruising speed or is coasting. The motor-generator is used as a variable power input device during vehicle acceleration to allow steady state operation of the internal combustion engine in one operating mode and to minimize throttle excursions in another mode. When the vehicle is in steady state operation, or is coasting, the motor-generator is switched to its generating function for battery charging purposes.
From the above, it will be seen that this particular prior art system relies on the operation of the internal combustion engine as the main source of power and uses the motor-generator to reduce, or eliminate, engine RPM fluctuations. Although this will reduce fuel usage and pollution somewhat, the reduction is not significant enough to warrant the high cost of converting to such a system. Further, this system cannot be used as a purely electric drive system at any time, and in particular at the time of steady state, or coasting of the vehicle when electric drive is most desirable due to minimal power drainage from the batteries at those times. This prior art system cannot be used as an electric drive system, with a power boost when needed from the internal combustion engine due to the fact that the generator must be locked against rotation and electrically disconnected from the system when the vehicle is operating in the steady state, or is coasting, and the motor-generator must be switched to its generating mode at those times for battery charging purposes. The generator is locked out of the system to prevent reverse driving thereof which, in addition to possible ruining the generator, causes the entire system to be thrown into an unstable state due to the free running of the generator in the reverse direction causing the bulk of the output power from the internal combustion engine to be delivered to the generator and very little, if any, to the system output shaft.